Tantalum carbide alloy



Patented Jan. 12, 1937 UNITED STATES OD KEFEHENL E PATENT OFFICETANTALUM CARBIDE ALLOY Clarence W. Balke, Highland Park, Ill., assignorto Ramet Corporation of America, North Chi- No Drawing.

Serial No. 659,834

20 Claims.

This invention relates in general to alloys, and has more particularreference to a novel and an improved alloy suitable for, but not limitedto, the formation of tools and other implements.

For so much of the subject matter herein dis' closed, which is alsodisclosed in either of my copending United States Letters Patentapplications entitled Tantalum carbide alloy, Serial No. 439,227, filedMarch 26, 1930, and entitled Method of making hard alloys for cuttingtools, Serial No. 439,228, filed March 26, 1930, the latter having sincematured into Patent 1,937,185 dated Nov. 28, 1933, I claim the priorityof said patent applications.

Among the objects of the invention is the provision of a novel alloywhich, when used as a cutting tool, will be substantially non-cratering,that is, substantially free from undue wear or adherence between thechips from the work and the upper face of the tool when the tool is usedfor rapidly turning or cutting materials asdiiiicul so to work as steel.

Among other objects of the invention are the provision of a hard alloywhich includes as its predominant constituent, tantalum and carbon,substantially all of the carbon being in the form of a carbide oftantalum, and where desired, some of the tantalum remaining uncarburizedafter the formation of the carbide; the provision in such an alloy of anauxiliary metal or metals making up a minor percentage by weight-of theentire alloy, and having a melting temperature less than that of thetantalum carbide; and the provision of a hard alloy including thetantalum, carbon, and the auxiliary material and having sufilcienthardness, toughness, and strength to be suitable as a working portionfor lathe tools and tools for other metal cutting or working machines,which working portion will retain such hardness, strength, and.toughness even at the relatively high temperatures frequently developedin use.

Other objects and advantages of the invention will be apparent from thefollowing description.

One of the best alloys, according to the invention, comprises tantalumand carbon in the proportion of from 93.8% to 95% by weight of tantalum,to from 6.2% to by weight of carbon, substantially all of the carbonbeing combined with the proper amount of the tantalum to form tantalumcarbide according to the formula TaC,

and the carbon and tantalum together making A specific alloy within thepurview of this invention comprises tantalum and carbon in theproportion of 94.25% by weight of tantalum to 5.75% by weight of carbon,substantially all of the carbon being combined with sufficient tantalumto form tantalum carbide according to the formula TaC, the alloyincluding in addition to the tantalum and carbon by weight of nickel.The invention is not limited to the precise percentages or proportionsand the exact ingredients mentioned above, but contemplates that thetantalum and carbon together may range from barely a predominatingamount by weight up to 97% by weight of the entire alloy, and that theproportion of tantalum to carbon may be so calculated that whilesubstantially all of the carbon is used to form tantalum carbide, someof the tantalum remains uncarburized to promote toughness in the finalalloy. Of course, this uncarburized tantalum may be provided for byhaving an excess of tantalum for that required to form the carbide, orit may be added as free metal after the carbide has been formed.

Furthermore, while nickel is specifically mentioned as the auxiliarymetal in the examples given above, the invention contemplates the use ofany other metal or metals which have a melting temperature less thanthat of tantalum carbide, and which will wet the carbide or will alloy,at least to some extent, with the carbide at relatively low temperaturesas compared with the melting temperature of tantalum carbide. Asexamples of such metals for the auxiliary material, I may mention inaddition to nickel,- iron,

DEHPRLIE? KUUWE cobalt, manganese, chromium, palladium, plat- One methodwhich I have found suitable for combining the above mentionedingredients is to start with tantalum carbide powder to which, wheredesired, tantalum is added or to start with a mixture of tantalum powderand carbon powder in the desired proportions to produce tantalum carbideaccording to the formula TaC with or without some free tantalum. Wherethe tantalum is first mixed with the carbon powder, the tantalum andcarbon are combined by heat and degasified in order to remove or toexclude such embrittling impurities as oxygen from the tantalum carbide.In other words, the tantalum. and carbon in finely divided form aredegasified by a heat treatment in vacuo and the carbide powders areintermixed with one or more of the auxiliary metals from the classincluding nickel, chromium -dients, but also serves and manganese infinely divided form. This mixture of tantalum carbide and the auxiliarymetal with or without tantalum is pressed into workable bodies which areheat treated in vacuo to a temperature sufficient to form the alloy.

When these pressed bodies are heated in vacuo to a temperature at whichthe particular auxiliary metal or metals are molten or plastic, theauxiliary metal or metals from the class including nickel, chromium, andmanganese, will bring about or will cause a shrinkage of the bodies intoa sound solid alloy substantially free from porosity and voids. Thetemperature of the combining heat treatmentwill vary according to theamount of and the particular auxiliary metal or metals from the groupincluding nickel, chromium and manganese employed in the alloy.Ordinarily, however, this temperature is less than the meltingtemperature of the added auxiliary metal, but not less than 1350" C.This vacuum heat treatment serves not only to combine the ingreto removesuch embrlttling impurities as oxygen, which may have been absorbed,occluded, or otherwise picked up by the fine powders during thepreceding stages preliminary to the formation of the final alloy.

I have found that tools of my novel alloy when used for rapidly turningor cutting materials as diflicult so to work as steel, are substantiallyfree from that objectionable action known as cratering, or the unduewearing away of the tool material just back of the cutting edge of thetool, or adherence between the work chips and the tool materialresulting in the removal of some tool material from the face of thetool.

Thus, an alloy of one or more metals of the class including nickel,chromium and manganese, and a refractory metal carbide is formed whichhas a homogeneous and substantially nonporous structure and which willbe substantially free from cratering. This alloy retains the propertiesof sufficient hardness, mechanical strength and toughness for use intools, even at the temperatures frequently developed in its use as alathe, planing, or other cutting or metal working tool.

Illustrative of the advantages of this improved alloy, I have found thattools made thereof are extremely hard, and that in taking heavy cuts ona hard manganese steel, the tools did not heat so rapidly as othertools, and apparently offered a minimum resistance to the relativemovement of the material being cut. In addition, the tools did notcrater while operating under this exceedingly heavy duty.

While I have described as a preferred embodiment of my invention analloy comprising tantalum carbide with or without free tantalum, it willbe understood that the invention contemplates the use of other hardrefractory metals and their carbides. In this connection I haveparticular reference to the refractory metal columbium and a carbidethereof. I do not, therefore, wish to be limited to the preciserefractory metal or carbide thereof set forth, but contemplate thatcolurnbium carbide and/or columbium metal may replace tantalum carbideand/or tantalum, respectively, in whole or in part in my alloy, and Idesire to avail myself of all such changes within the scope of theappended claims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States is:

1. An imporous tool comprising an alloy consisting of deoxidizedtantalum carbide predominating by weight therein, and a metal of theiron group united therewith.

2. An imporous tool comprising'zan alloy consisting of deoxidizedtantalum carbide predominating by weight therein, and more than onemetal of the iron group united therewith.

3. A hard and tough alloy comprising from 3% to 15% by weight of a metalof the iron group, and the remainder tantalum carbide having from 5% to6.2% by weight of carbon.

4. A cutting tool comprising 10% by weight of nickel, the remaindertantalum and carbon in the proportion of 5.75% by weight of carbon to94.25% by weight of tantalum.

5. -A hard and tough alloy composed of from 3% to 15% by weight ofnickel, and tantalum carbide making up the remainder of said alloy.

6. A hard and tough alloy comprising tantalum carbide, includingtantalum and carbon in the proportion of from 93.8% to 95% by weight oftantalum to from 6.2% to 5% by weight of carbon, and having in additionthereto a metal of the iron group making up the remainder of said alloyand ranging from 3% the entire alloy.

7. A hard and tough tool having a low heat conductivity, comprisingtantalum, carbon combined therewith in the proportion of from 93.8% to95% by weight of the tantalum to fr'om.6.2% to 5% by weight of thecarbon, the the carbon together making up not more than 97% by weight ofthe'tool, but not less than a predominating amount by weight of thetool, and a metal of the iron group combined with the tantalum andcarbon and making up from 3% to 15% by weight of the tool.

8. A hard and tough tool having a low heat conductivity, comprisingtantalum, carbon combined therewith in the proportion of from 93.8% to95% by weight of tantalum to from 6.2% to 5% by weight of the carbon,the tantalum and the carbon together making up not more than 97% byweight of the tool, but not less than a predominating amount by weightof the tool, and more than one metal of the iron group combined with thetantalum and carbon and making up from 3% to 15% by weight of the tool.

9. A hard alloy comprisingfrom' to 97% by weight of tantalum carbide andfrom 15% to 3% by weight of an auxiliary metal having a meltingtemperature below the melting temperature of the tantalum carbide andadapted to combine with tantalum at 'a relatively low temperature ascompared with the melting point of the tantalum carbide.

10. A hard alloy comprising from 85% to 97% by weight of. tantalumcarbide and from 15% to 3% by weight of nickel.

11. An alloy comprising a refractory metal from the group consisting oftantalum and columbium, carbon combined therewith in the proportion offrom 93.8% to by weight of said refractory metal to from 6.2% to 5% byweight of carbon, said carbon being combined with'said refractory metalto form a carbide therewith, and from 3% to 15% by weight of nickelmakingup the remainder of the alloy. I

12. A hard and tough alloy comprising from 3% to 15% by weight of one ormore metals of the iron group and the remainder one or more carbides ofa hard refractory metal from the group consisting of tantalum andcolumbium.

13. A sintered, hard, tough, metal composition consisting substantiallyof tantalum carbide and a binder material, said binder to 15% by weightof tantalum and 30 material contain- 76 W055 Ktttlitlibt 'ent in saidcomposition in appreciable but minor quantities.

15. A sintered composition containing about" 3% to about 25% of ametallic binder material,

the remainder of said composition consisting substantially oi columbiumcarbide, said binder material having a lower melting point than saidcarbide and consisting mainly of metal of the iron group.

16. A sintered, hard, tough, metal, composition consisting substantiallyof tantalum carbide and nickel, the nickel comprising from about 3% toabout 20% of said composition.

17. A sintered, hard, tough, metal composition consisting substantiallyof tantalum carbide and metal of the iron group, said metal of the irongroup comprising fromabout 3% to about 20% of said composition.

18. A sintered, hard, tough, metal composition consistingsubstantiallyof tantalum carbide and cobalt-the cobalt comprising from about 3% toabout 20% of said composition.

19. A sintered, metal composition containing about 3% to about 20% of abinder material, the remainder of said composition consistingsubstantially of tantalum carbide, said binder having a lower meltingpoint than said carbide.

20. A sintered composition consisting substantially of hard, metalcarbide particles and a metallic cementing medium therefor, one of theprincipal ingredients 01' said composition being tantalum carbide.

CIARENC'E W. BALKE.

OEHHUH

